The present disclosure relates to a fan.
A fan is a device for producing an air flow. An axial fan is a type of fan which takes in and discharges air along a shaft of the axial fan.
An axial fan includes a plurality of blades disposed on an outer surface of a hub. When an axial fan rotates, air flows from a leading edge of a blade to a trailing edge of the blade, along a positive pressure surface of the blade.
As a conventional axial fan rotates, the greatest amount of pressure is applied to center portions of the positive pressure surfaces of the blades, and the lowest pressure is applied near the trailing edges of the blades. As the fan rotates, air separates from the blades at the trailing edge of each blade, which creates noise. This air separation also reduces the blowing performance of the axial fan.
For the purpose of improved blowing performance, the hubs of some conventional fans have a cone-like shape. However, a problem with such fans is that a die-lock often occurs during the molding process. That is, when a fan is molded using a two-plate mold, the mold plates are often difficult to separate after the molding process. This problem can increase the manufacturing costs for the fans.
Characteristics of a blade which affect the blowing performance and noise characteristic of a fan include a sweep angle, a rake angle, a pitch angle, a camber, and a position of the camber.
FIG. 1 is a plan view illustrating a sweep angle Ψ of a related art axial fan.
Referring to FIG. 1, a point P1 is defined as a center point of a portion of a blade 50 which is connected to a hub 10. A point P2 is defined as a center point of an outer edge 58 of the blade 50. A sweep angle Ψ is defined as an angle between a first imaginary line connecting the point P1 to the center of the hub 10 and a second imaginary line connecting the point P2 to the center of the hub 10.
FIG. 2 is a perspective view illustrating a rake angle γ of the related art axial fan.
Referring to FIG. 2, the rake angle γ is defined as an angle between a third imaginary line connecting the point P1 to the point P2 and a fourth imaginary line which is perpendicular to a rotation axis of the hub 10. The rake angle γ refers to how the blade 50 is inclined from the fourth imaginary line, which is perpendicular to the rotation axis of the hub 10.
FIG. 3 is a perspective view illustrating a pitch angle θ of the related art axial fan.
Referring to FIG. 3, the pitch angle θ is defined as an angle between a fifth imaginary line which connects the ends of the portion of the blade 50 connected to the hub 10 and a sixth imaginary line which is parallel to the rotation axis of the hub 10. The pitch angle θ refers to how much the blade 50 is twisted relative to the rotation axis of the hub 10. A camber is defined as the amount of concavity of a positive pressure surface 51 of the blade 50 with respect to a negative pressure surface 52 of the blade 50.